Abstract: A delay-locked loop (DLL) has a fractional phase frequency (PF) detector that reduces false locking and harmonic locking. The PF detector has a trunk, an upper branch, a lower branch, and a logic module. A delay line provides the PF detector a set of fractional phase-delayed clock signals that are used to prime and/or activate corresponding flip-flops of the trunk, upper branch, and lower branch in a sequence. The use of flip-flops in the lower branch activated by different fractional phase-delayed clock signals avoids false locking and harmonic locking over a wider range of initial delay magnitudes than conventional DLLs.

Abstract: A clock generator includes a diagnostic circuit that includes first and second muxes, first and second comparators, a logic gate, and a counter. The first mux receives first and second voltage signals and outputs a first intermediate signal based on a control signal. The second mux receives third and fourth voltage signals and outputs a second intermediate signal based on the control signal. The first and second comparators compare the intermediate signals with a first signal that is indicative of a DC value of the clock signal for generating first and second comparison signals. The logic gate receives the first and second intermediate signals and generates a control signal. The counter receives the clock signal and the control signal and generates a clock ready signal that is indicative of stability and quality of the clock signal.

Abstract: A buffer circuit includes an inverter and a level-shifter. The inverter receives a first oscillating signal at a first voltage level and generates an inverted version of the first oscillating signal at a second voltage level. The level-shifter receives a second oscillating signal at a third voltage level, which has a phase difference from the first oscillating signal, and the inverted first oscillating signal, and generates a buffer output signal at a fourth voltage level.

Abstract: A level shifter circuit for level shifting voltages of signals crossing multiple circuit domains includes an input stage and a driver stage. The input stage receives an oscillating signal generated by a ring oscillator and generates an inverted oscillating signal. The differential oscillating signals are provided to the driver stage, which level shifts a voltage level of the oscillating signal to a level of a supply voltage of the ring oscillator.

Abstract: A phase locked loop (PLL) system generates an oscillator signal by providing a fixed control voltage to a programmable voltage to current converter having switch selection inputs and a variable current output. Logic values are provided to the switch selection inputs to adjust a control current at the variable current output and a frequency of the oscillator signal is adjusted based on the control current. The logic values are fixed when a first condition is reached, which is based on the frequency of the oscillator signal, a division factor, and an input reference signal frequency. The fixed control voltage provided to the programmable voltage to current converter is then replaced with a charge pump control voltage based on an error signal. The error signal is based on a comparison of the input reference signal frequency and a fraction of the oscillating frequency.

Abstract: A level shifter circuit for level shifting voltages of signals crossing multiple circuit domains includes an input stage and a driver stage. The input stage receives an oscillating signal generated by a ring oscillator and generates an inverted oscillating signal. The differential oscillating signals are provided to the driver stage, which level shifts a voltage level of the oscillating signal to a level of a supply voltage of the ring oscillator.

Abstract: A phase-locked loop (PLL) generates an oscillator signal based on an input reference signal. A voltage-to-current converter converts a control voltage to a first current. A current-controlled oscillator generates the oscillator signal based on the first current. A dual charge pump circuit generates first and second charge pump currents having a predetermined ratio, based on a second current generated by a current mirror circuit and an error (feedback) signal. An active loop filter generates the control voltage based on the first and second charge pump currents. The active loop filter includes an input capacitance that varies with a variation in the predetermined ratio of the charge pump currents. The active loop filter also includes a transconductance stage having a transconductance that varies based on a third current generated by a current mirror circuit. The PLL bandwidth is independent of PVT variations and dependent only on the frequency of the input reference signal.

Abstract: A relaxation oscillator for generating oscillator signal includes a ramp voltage generating circuit, a reference voltage generating circuit, a reference voltage switching circuit, and a digital logic circuit. The reference voltage generating circuit generates one or more reference voltages and the ramp voltage generating circuit generates one or more ramp voltages. The ramp voltages are compared with each of the reference voltages by sequentially switching the reference voltages using a reference voltage switching signal generated by the reference voltage switching circuit. The oscillator signal is generated by the digital logic circuit based on the results of the comparisons.

Abstract: A relaxation oscillator for generating oscillator signal includes a ramp voltage generating circuit, a reference voltage generating circuit, a reference voltage switching circuit, and a digital logic circuit. The reference voltage generating circuit generates one or more reference voltages and the ramp voltage generating circuit generates one or more ramp voltages. The ramp voltages are compared with each of the reference voltages by sequentially switching the reference voltages using a reference voltage switching signal generated by the reference voltage switching circuit. The oscillator signal is generated by the digital logic circuit based on the results of the comparisons.

Abstract: A phase-locked loop (PLL) generates an oscillator signal based on an input reference signal. A voltage-to-current converter converts a control voltage to a first current. A current-controlled oscillator generates the oscillator signal based on the first current. A dual charge pump circuit generates first and second charge pump currents having a predetermined ratio, based on a second current generated by a current mirror circuit and an error (feedback) signal. An active loop filter generates the control voltage based on the first and second charge pump currents. The active loop filter includes an input capacitance that varies with a variation in the predetermined ratio of the charge pump currents. The active loop filter also includes a transconductance stage having a transconductance that varies based on a third current generated by a current mirror circuit. The PLL bandwidth is independent of PVT variations and dependent only on the frequency of the input reference signal.

Abstract: A duty cycle correction circuit for correcting the duty cycle of a clock signal generated by a clock generator includes a complementary buffer chain, level shifter circuits and a self-bias circuit. A clock signal with a distorted duty cycle and its complement are provided to the level shifter circuits. The level shifter circuits reduce the magnitude of voltage of the clock signal and the complement and generate level shifted signals. The level shifted signals are provided to a differential amplifier that generates a control signal indicating the magnitude of distortion in the duty cycle. The control signal is used to correct the duty cycle of the clock signal. The self-bias circuit is used to bias the differential amplifier.

Abstract: A duty cycle correction circuit for correcting the duty cycle of a clock signal generated by a clock generator includes a complementary buffer chain, level shifter circuits and a self-bias circuit. A clock signal with a distorted duty cycle and its complement are provided to the level shifter circuits. The level shifter circuits reduce the magnitude of voltage of the clock signal and the complement and generate level shifted signals. The level shifted signals are provided to a differential amplifier that generates a control signal indicating the magnitude of distortion in the duty cycle. The control signal is used to correct the duty cycle of the clock signal. The self-bias circuit is used to bias the differential amplifier.

Abstract: A programmable digital clock signal frequency divider module has a module clock input, module clock output, a scaling factor input, two programming inputs, and a tertiary input. A primary divider module with a primary divider module output and a clock input are coupled to the module clock input. A secondary divider module includes a multiplexer and a divide by two latch with a latch clock input coupled to the primary divider module output. In operation, logic values applied to the scaling factor input, and the programming inputs, result in the primary divider module processing a first sequence of cycles of a primary digital clock signal into a first base clock signal and processing a subsequent second sequence of cycles into a second base clock signal. The first base clock signal and the second base clock signal provide a sequence of clock pulses to the secondary divider module.

Abstract: A phase-locked loop (PLL) system generates an oscillator signal based on an input reference signal. A calibration circuit generates a calibration current, and a voltage-to-current converter converts a control voltage into a first current. A current-controlled oscillator generates the oscillator signal based on the first current and the calibration current. A charge pump circuit, which is connected to a phase detector, the voltage-to-current converter, and the calibration circuit, generates a charge pump current based on the first current and the calibration current. The charge pump current is used to generate the control voltage based on an error signal.

Abstract: A phase-locked loop (PLL) system generates an oscillator signal based on an input reference signal. A calibration circuit generates a calibration current, and a voltage-to-current converter converts a control voltage into a first current. A current-controlled oscillator generates the oscillator signal based on the first current and the calibration current. A charge pump circuit, which is connected to a phase detector, the voltage-to-current converter, and the calibration circuit, generates a charge pump current based on the first current and the calibration current. The charge pump current is used to generate the control voltage based on an error signal.

Abstract: A level shifter (10) includes a first transistor (12) having a gate configured to receive a first input signal, and a second transistor (14) having a gate configured to receive a second input signal. A first feedback circuit is connected to drains of the first transistor (12) and the second transistor (14). A second feedback circuit is connected to the first feedback circuit.